Echocardiography in congenital mitral valve regurgitation--the liaison between cardiologist and surgeon.

Congenital heart diseases are broadly defined as those cardiac anomalies that are present at birth. By their very nature, such defects have their origin in embryonic development. Congenital mitral valve regurgitation is a rare disease occurring in infancy or childhood. In up to 60% of cases, congenital anomalies of the mitral valve occur in association with other cardiac lesions, and often more than one component of the mitral apparatus is involved. The true incidence of congenital mitral valve regurgitation (MVR) is difficult to determine accurately (0.21–0.42% from total mitral valve regurgitations); isolated congenital mitral regurgitation is uncommon. The Carpentier classification of congenital mitral valve disease is the most commonly used nomenclature based on a functional analysis of the mitral valve leaflet. The contemporary anatomic classification has the advantage of minimizing observer variability in the diagnosis and it offers a much better liaison between the cardiologist and surgeon.

Historically, the emergence of two-dimensional echocardiography must be viewed as a milestone in the diagnostic approach to congenital heart disease. The tomographic nature of the technique and its great number of imaging planes permit the anatomy and relationships of the cardiac structures to be defined, even in the presence of complex congenital malformations. For the noninvasive assessment of cardiac structure and function, echocardiography plays a prominent role as the most accurate and widely applied method. When details of the clinical history are unavailable, the echocardiographer is often called on to determine which surgical procedures have been performed. The options for further intervention often depend on the echocardiographic results [1,2].
For a good and useful evaluation, echocardiographic exam must take into account the anatomic and functional aspects of mitral valve, in a tight connection. To obtain a comprehensive and accurate description of the whole mitral apparatus it is useful to have a systemic approach when performing transthoracic echocardiography and multiplane transesophageal echocardiography examination.
The anatomic structure of mitral apparatus is complex and sometimes difficult to describe in echocardiographic exam [3].
Anatomically, the mitral valve consists of an annulus, leaflets, chordae tendineae, and papillary muscles. The mitral annulus is an integral part of the fibrous skeleton of the heart. The normal mitral valve has two leaflets, anterior and posterior, that act in conjunction with the subvalvular apparatus as one functional unit. The larger anterior (i.e., septal or aortic) leaflet attaches to 150 degrees of the annulus, and is squat and trapezoidal in shape. As a consequence of being in fibrous continuity with the aortic valve, it forms the posterior boundary of the left ventricular outflow tract. The posterior (i.e., mural) leaflet is narrower and occupies 210 degrees of the annulus. Two natural indentations in the posterior leaflet produce three segments, which subdivide it into lateral, central and medial scallops. The mitral valve leaflets are separated by the anterolateral and posteromedial commissures. Beneath the commissures lie two corresponding papillary muscles, which are extensions of the subendocardial ventricular myocardium. Chordae tendineae from the papillary muscles insert on both sides of the corresponding commissure, so each valve leaflet receives chordae from both papillary muscles.
Considerable variation can be found in the morphology of the normal mitral valve [4,5]. It is now widely recognized that the function of the mitral valve depends on the normal function and integrity of the leaflets, annulus, chordae tendineae, papillary muscles, and subjacent left ventricular myocardium. Abnormalities in any of these components, either individually or in combination, produce dysfunction of the mitral valve unit.
It should be expected that medical and surgical practice use prevalently an anatomic classification. However, the Carpentier classification [6] of congenital mitral valve disease (Table I) is the most commonly utilized nomenclature both in medical and surgical practice.
This 1976 classification is predicated on a functional analysis of the mitral valve leaflet. However, there are two limitations of this classification, which can produce observer variability, and therefore potential inconsistency in data reporting. Firstly, a purely stenotic or insufficient valvar lesion is rarely observed. Secondly, the surgical literature has generally divided, reported, and risk stratified congenital mitral valve lesions based on stenosis versus insufficiency, not leaflet function [4].
In addition, the Carpentier classification was developed before routine two-dimensional echocardiography was available. Functional evaluation of the leaflets by direct vision in the operating room may be difficult, despite saline insufflation of the flaccid left ventricle [4].
Accurate and thorough preoperative echocardiography becomes mandatory to define lesions based on leaflet motion and to effect the appropriate repair. Individual interpretations of the functional anatomy introduce variability, which makes the reliability and reproducibility of a classification difficult [4,8,9].
At present, transesophageal echocardiography provides considerable information regarding mitral valve structure and function. Intraoperative echocardiographic monitoring of mitral valve surgery has become a routine practice in most cardiac centers. Perioperative assessment of valve anatomy by transesophageal approach provides detailed anatomical imaging [9].
Surgeons now have much more information before the valve is inspected. This permits preoperative classification, which may be enhanced by direct observation of the valve at the time of operation.
Within the context of criticisms for Carpentier functional classification of congenital mitral valve diseases and from practical necessity, S. N. Mitruka et al. [4] ( Table II) proposed a contemporary unifying anatomic classification for congenital abnormalities of the mitral valve based on a consideration of whether the valve is stenotic or insufficient.
The adoption of an optimal standard nomenclature that could be widely utilized, consistent, and reproducible would minimize observer variability in the diagnosis. This classification makes the issues of leaflet function as a consequence of the altered valvar anatomy. This, in turn, allows a segmental and systematic approach for considering the therapeutic options [10,11,15].
The anatomic contemporary classification for congenital mitral valve disease is presented below (

Combination of two or more of the others three types
In virtue of this classification, we present some personal echocardiographic images with congenital mitral valve regurgitation, as it follows: -Type 1 (supravalvar), an abnormality of the mitral valve above the level of the leaflets or annulus, is illustrated in Fig.1 by a mitral supravalvular ring (a circumferential ridge of endocardial tissue attached to the anterior leaflet below its insertion on the annulus). -Type 4 (mixed), an abnormality of the mitral valve that is described as a mixture or combination of two or more of the above three types, described in Fig. 7 by: annulus dilatation, excessive tissue on the leaflets and elongated chordae tendineae.  [4,10,11] A B C D

A B
The therapeutic options for congenital mitral valve disease are somewhat limited [12,13]. An operation on the mitral valve requires excellent exposure and considerable attention to detail.
The echocardiography can offer preoperative important features and allows the characterizations of the lesions based on both accepted classifications: the functional and the anatomical one. Currently, Doppler echocardiography plays an important role in the early determination of the type of surgery that may be performed for the correction of the mitral valve regurgitation [14][15][16]. The morphological and functional aspects obtained on Doppler transthoracic and transesophageal echocardiography usually allow

A B
estimating with 85% the possibility of performing mitral valvuloplasty and its success in patients with myxomatous degeneration, particularly when the posterior leaflet is the most impaired one [17][18][19].
There is no truly satisfactory substitute for the mitral valve in a patient of any age. The limitations of replacing the mitral valve with a mechanical valve in infants and children are well recognized [10]. Techniques for the repair of the mitral valve have become increasingly sophisticated in recent years [11] and may provide improvement in mitral valve function which permits delay in mitral valve replacement. It is possible that homograft replacement of the mitral valve will be a useful technique at some time in the future, but the technique must be considered investigational at the present time.
Often, infants and children are referred for mitral valve operation in the absence of obvious symptoms. Gross cardiomegaly and dilatation of the left atrium in a seemingly asymptomatic child may provide an adequate basis for operation if the preoperative echocardiographic analysis suggests that the valve is amenable to repair.
In patients with a markedly abnormal valve or in those who have previously undergone repair, mitral valve replacement may be the only option [20].
In general, most cardiologists and surgeons wait longer before referring a patient for mitral valve replacement than they would for a first time attempt at mitral valve repair. Thus, surgical intervention is considered when symptoms become severe or when exercise limitations become unacceptable. Valve repair is the optimal course of action. Mitral valve replacement is considered a last resort [21].

Conclusions
The classification for congenital mitral valve regurgitation based dominantly on anatomic considerations offers useful medical and surgical details for the most appropriate mitral valve correction (valve repair being the optimal one). The Carpentier classification based on functional analysis of mitral valve leaflet continues to be the traditional classification, and may be used in addition to the anatomic nomenclature.